1. Field of the Invention
The present invention relates to: an organic-inorganic composite material containing a triazine ring, which is a cured material of a cyanate ester compound and has excellent electrical insulation, thermal stability and adhesiveness to a metal material; an electrical device using the organic-inorganic composite material; a semiconductor device using the organic-inorganic composite material; and a varnish which gives the cured material.
2. Background Art
The power densities of electrical and electronic devices are increasing yearly, and in the operating environment of inverters and power generators, the temperature is increased and the intensity of the electrical field is also increased. Accompanying this, there is a demand that an insulating resin material constituting such a device should have high thermal stability, high voltage resistance, and high adhesive strength to a heterogeneous member such as a metal.
It is known that a layered clay mineral (clay) typified by montmorillonite or smectite has excellent electrical insulation and can impart excellent properties such as impartment of flame retardancy, reduction in dielectric constant, improvement of insulation life, increase in mechanical strength and reduction in thermal expansion by combining any of various resin materials such as polyolefins, nylons, polystyrenes and epoxy resins. In order to allow a material to exhibit these excellent properties, it is necessary to form a composite of a clay and a resin, and in order to form such a composite, it is necessary to select a clay which is appropriately subjected to interlayer modification depending on the type of resin to be combined.
For example, Patent Document 1 (JP-A-2006-265507) discloses the impartment of flame retardancy by forming a composite of a polyolefin and a clay organified with ammonium ions, Patent Document 2 (JP-A-2005-251543) discloses the improvement of insulation life of an epoxy resin by a clay subjected to interlayer modification with quaternary ammonium ions, Non-Patent Document 1 (“Effect of Bentonite Modified with Novel Phosphonium on the Physical Properties of Acid Anhydride-Cured Epoxy Resin/Clay Nanocomposites”, Journal of Network Polymer, (2009) Vol. 30, No. 2, pp. 69-76) discloses a reduction in thermal expansion of an epoxy resin by montmorillonite subjected to interlayer modification with phosphonium ions, and Non-Patent Document 2 (“Development of Clay Minerals/Organic Polymer Nano-hybrid Materials”, The Journal of The Chemical Society of Japan, (2000), No. 9, pp. 605-611) discloses an increase in strength of a nylon by montmorillonite subjected to interlayer modification with 1,2-aminolauric acid.
However, although a clay dispersion technique employing a conventional interlayer modification method is effective in thermoplastic resins or some thermosetting resins, the technique cannot be applied to cyanate ester cured resins having high thermal stability. The invention is directed to a material, which could be also called a support for uniformly mixing and dispersing clay in a cyanate ester cured resin having high thermal stability and a curing catalyst for the compound. Further, a clay to be used in the material can serve not only as a catalyst, but also as an inorganic filler for a cured material containing a triazine ring, and gives high electrical insulation, high thermal stability (a glass transition temperature of 200° C. or higher), high adhesiveness to a metal and high mechanical strength to a composite material.